(1) Technical Field
The present invention relates to recoverable energy absorbers, such as are used non-destructively and re-usably for absorbing energy in automotive and non-automotive applications. It is to be understood that the present disclosure is not limited to automotive vehicles. Related technical fields could include head-protecting crash and sports helmets of various kinds.
(2) Background Art
Many different geometrically shaped thermoformed energy absorbers are known, such as those described in U.S. Pat. Nos. 6,017,084; 6,221,292; 6,199,942; 6,247,745; 6,679,967; 6,682,128; 6,752,450; 7,360,822; 7,377,577; 7,384,095; and 7,404,593. These absorbers are said to provide dynamic reactionary force characteristics that produce a relatively “square wave” shape when observing their reactionary force properties as a function of deflection.
Often, these formed energy absorbers lie between a Class-A surface which may take a hit (such as a bumper fascia, a headliner, or a door trim panel) and a rigid sheet metal structure (such as a vehicle frame or an engine block) in automotive applications. The energy absorber is typically designed with a 3-5 mm gap from one surface and is attached to another surface. However, in some instances it becomes necessary to increase the overall depth of the energy absorber so that the unattached surface is closer to the other surface during normal vehicle operation. Further, product variation may cause some areas to become closer than the optimal gap distance. When the energy absorber lightly contacts the opposing surface, due to relative movement between vehicle components, a buzz, rattle, or squeak can be heard, which customers object to or find annoying. This noise may occur because a flat hard plastic surface can tap or slide against the opposing structure.
Materials are sometimes added to or placed adjacent to energy absorbers in an effort to solve this problem. For example, in the past, a fabric pad, foam padding, or other kinds of flexible material have been added to one of the surfaces responsible for the noise in an effort to lessen or eliminate the severity of the buzzing or tapping, and/or to eliminate the possibility of one surface translating into the other (or translating across the other, causing a squeak). However, this requires the purchase and assembly of at least one separate component, causing added complexity, cost, and added mass.